Pamukkale, meaning "cotton castle" in Turkish, is a natural site and attraction in south-western Turkey in the Denizli Province. Pamukkale is located in Turkey’s Inner Aegean region, in the River Menderes valley, which enjoys a temperate climate over the greater part of the year. (Wikipedia)
Travertine is a kind of rock which is formed as calcium bicarbonate precipitates out of hot spring water. It may be formed in many ways under different atmospheric conditions. Geological activity of the past affected a large area in which the Pamukkale thermal springs are found. There are 17 thermal sources in this special area with temperatures ranging between 35-100°C. The source of Pamukkale is only one unit of that whole area. The thermal water flows to the top of the cascades by a 320-meter-long channel and then flows on the cascades about 240-300 m. CaCO3 begins to precipitate on the cascades as the carbon dioxide evaporates, but in the beginning the precipitate is soft like gel. It needs time to completely dry and harden. In order to protect the cascades from destruction and to preserve their natural beauty, entrance to the travertine area has been prohibited.